Method and apparatus for altering conduction properties in the heart and in adjacent vessels

ABSTRACT

Method and apparatus for treating conductive irregularities in the heart, particularly atrial fibrillation and accessory path arrythmias. An ablative catheter is positioned relative to an inter-atrial electrical pathway, or a vicinity of accessory paths such as the coronary sinus or fossa ovalis, and actuated to form a lesion that partially or completely blocks electrical conduction in at least one direction along the pathway.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application Ser.No. 60/287,768 entitled “Catheterization Method of Altering ConductionProperties Along Pathways in the Heart and in Vessels in ConductiveCommunications with the Heart,” filed May 1, 2001, which is incorporatedherein by reference.

FIELD OF THE INVENTION

The invention relates to one or more catheterization methods of alteringconduction properties along pathways in the heart, and in vessels inconductive communication with the heart, and is particularly related tomethods of ablative catheter treatment of atrial fibrillation andarrhythmias of accessory pathways.

BACKGROUND OF THE INVENTION

The human heart is a very complex organ, which relies on both musclecontraction and electrical impulses to function properly. Electricalimpulses travel through the heart in a desired sequence so that thevarious chambers receive and pump blood in the proper order. Withrespect to the atria, normal excitation is propagated in a right atriumto left atrium direction via inter-atrial conduction pathways, includingthe coronary sinus, fossa ovalis, and Bachmann's bundle.

Abnormal inter-atrial electric flow, such as left-to-right conduction,may pose serious health risks to a patient including atrialfibrillation. Catheter ablation, that is the application of energy at adistal portion of a catheter positioned within or about the heart, or avessel in electrical communication with the heart, to form lesions thatalter conductive properties in the heart, is known for treating atrialfibrillation. Such techniques have targeted the focal trigger of anatrial arrhythmia as well as reentrant circuits in the myocardium.

SUMMARY OF THE INVENTION

One illustrative embodiment of the invention is directed to a method oftreating atrial fibrillation. The method comprises providing a catheterincluding a distal portion having an arrangement for conductivealteration of an inter-atrial conductive pathway of the heart,positioning the distal portion of the catheter relative to a portion ofthe inter-atrial conductive pathway, and actuating the conductivealteration arrangement to alter the conduction of the inter-atrialconductive pathway.

Another illustrative embodiment of the invention is directed to a methodfor treating arrhythmia of an accessory pathway of the heart. The methodcomprises providing a catheter including a distal portion having anarrangement for conductive alteration of a portion of the heart and/orof a vessel in communication with the heart that is in the vicinity ofan accessory pathway, positioning the distal portion of the catheterrelative to the portion of the heart and/or of the vessel in thevicinity of the accessory pathway, and actuating the conductivealteration arrangement to alter the conduction of the accessory pathway.

A further illustrative embodiment of the invention is directed to amethod for treating a condition of the heart. The method comprises actsof introducing a catheter into the heart, the catheter having a braidedconductive member at a distal end thereof, forming a lesion on tissue ata selected location of the heart with the braided conductive member, andmeasuring the quality of the lesion with the braided conductive member.

Another illustrative embodiment of the invention is directed to acatheter having a braided conductive member. The braided conductivemember comprises one or more ablation filaments for applying ablativeenergy to a surface of a heart, and one or more mapping filaments formeasuring an electrical signal at a surface of the heart.

A further illustrative embodiment of the invention is directed to amethod for treating a condition of a heart. The method comprises an actof using a catheter having a braided conductive member to create alesion at a location selected from the group consisting of a wall of thecoronary sinus, a wall of the right atrium at the opening of thecoronary sinus, a wall of the right atrium at the fossa ovalis, and awall of the left atrium at the fossa ovalis.

Another illustrative embodiment of the invention is directed to a methodfor treating cardiac arrhythmia. The method comprises acts ofintroducing a catheter into the right atrium of a patient, the catheterhaving a braided conductive member at a distal end thereof, passing thebraided conductive member of the catheter through the inter-atrialseptum separating the right atrium and the left atrium, expanding thebraided conductive member in the left atrium of the patient, positioningthe braided conductive member so that the braided conductive membercontacts the inter-atrial septum, and applying energy to theinter-atrial septum via the braided conductive member to create a lesionon the inter-atrial septum.

A further illustrative embodiment of the invention is directed to amethod for treating cardiac arrhythmia. The method comprises acts ofintroducing a catheter into the right atrium of a patient, the catheterhaving a braided conductive member at a distal end thereof, passing thedistal end of the catheter through the inter-atrial septum separatingthe right atrium and the left atrium, expanding the braided conductivemember in the right atrium of the patient, positioning the braidedconductive member so that the braided conductive member contacts theinter-atrial septum, and applying energy to the inter-atrial septum viathe braided conductive member to create a lesion on the inter-atrialseptum.

Another illustrative embodiment of the invention is directed to a methodfor treating atrial fibrillation in a heart. The method comprises an actof using a catheter having a braided conductive member to ablate aregion of the heart that serves as an electrical pathway between thatleft atrium and the right atrium of the heart to alter the conductivityof the electrical pathway.

A further illustrative embodiment of the invention is directed to amethod for treating a condition of the heart. The method comprises actsof introducing a catheter into the heart, the catheter having a braidedconductive member, forming a lesion in the heart with the braidedconductive member, generating a pacing signal at a pacing electrode onthe catheter on a first side of the braided conductive member, anddetecting a received signal at a detection electrode on the catheter ona second side of the braided conductive member, wherein the receivedsignal is related to a quality of the lesion.

The features and advantages of the present invention will be morereadily understood and apparent from the following detailed descriptionof the invention, which should be read in conjunction with theaccompanying drawings, and from the claims which are appended at the endof the Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are incorporated herein by reference and in whichlike elements have been given like references characters,

FIG. 1 illustrates an overview of a mapping and ablation cathetersystem;

FIGS. 2 and 3 illustrate further details of the catheter illustrated inFIG. 1;

FIGS. 4-7 illustrate further details of the braided conductive memberillustrated in FIGS. 2 and 3;

FIGS. 8-10A illustrate, among other things, temperature sensing;

FIGS. 11-13 illustrate further details of the steering capabilities ofthe catheter;

FIGS. 14-17 illustrate further embodiments of the braided conductivemember;

FIGS. 18-19 illustrate the use of irrigation in connection with thecatheter;

FIGS. 20A-20E illustrate the use of shrouds;

FIG. 21 illustrates a guiding sheath that may be used in connection withthe catheter;

FIGS. 22-31 illustrate methods of using the catheter;

FIG. 32 illustrates the use of electrodes on the shaft of the catheter;and

FIGS. 33-34 illustrate the coronary sinus activation sequence before andafter ablation.

DETAILED DESCRIPTION

One embodiment of the present invention is a catheterization method foraltering the conductive properties of electrically conductive pathwaysin the heart and in vessels in electrical communication with the heart.The catheterization method is particularly suited for treating atrialfibrillation and arrhythmias of accessory pathways, e.g., the coronarysinus or fossa ovalis. In connection with treating atrial fibrillation,the catheterization method includes the step of altering electrical flowalong one or more of the preferential inter-atrial conduction paths:coronary sinus (“CS”), Bachmann's bundle and the fossa ovalis. Inconnection with treating arrythmias of accessory pathways, theconductive properties of the coronary sinus may be altered. Conductivealteration of the coronary sinus may encompass altering the conductivityof the wall of the coronary sinus, the ostium of the coronary sinus, orthe musculature surrounding the coronary sinus. Further, in connectionwith treating arrythmias of accessory pathways, the conductiveproperties of the fossa ovalis may be altered. Conductive alteration ofthe fossa ovalis may encompass altering the conductivity of the fossaovalis or the inter-atrial tissue around the fossa ovalis. Conductivealteration in connection with the inventive catheterization method doesnot necessarily mean the formation of a complete conduction block.Rather, a complete block, a partial block, or any therapeuticallyeffective change in conductive properties is within the meaning ofconductive alteration for purposes of this patent.

An ablative catheter is a preferred device for altering conductiveproperties in and around the heart. The ablative catheter is employed tocreate one or more lesions that may alter electrical flow along atargeted pathway in the heart and/or in a vessel in conductivecommunication with the heart. Energy may be employed to scarify theatrial conduction path or accessory path and may be generated by any ofa variety of sources including RF, DC, ultrasound, microwave, laser, orcryothermal. Non-electrical approaches to forming a lesion to disturbundesired left-to-right atrial impulses also are contemplated as shouldbe apparent to one of skill in the art. One or more lesions or otherconduction alternative structure may be applied at a location, in theinterior or the exterior of the heart or a blood vessel that is inconductive communication with the heart. The lesion or lesions mayextend circumferentially about or within a target blood vessel. Forexample, in connection with ablation of the coronary sinus, an annularlesion may be formed at or near the ostium. The circumferential lesionneed not be continuous; that is, scarred or necrotic segments may bespaced in a circumferential fashion even though one or more of thesegments is not contiguous with an adjacent segment. Other lesionarrangements also are contemplated so long as the lesion leads to areduction in undesired conduction. As observed above, although lesionformation by application of electrical energy is preferred, otherarrangements for producing lesions are contemplated as are other formsof conduction alteration structures.

The location of the undesired conduction path in the heart or adjoiningvessels may be determined by any suitable manner, including endocardialmapping. Mapping typically involves percutaneously introducing acatheter having one or more electrodes into the patient, passing thecatheter through a blood vessel (e.g. the femoral vein or artery) andinto an endocardial site (e.g., the atrium of the heart), anddeliberately inducing an arrhythmia so that a continuous, simultaneousrecording can be made with a multichannel recorder at each of severaldifferent endocardial positions. When the errant conduction path islocated, as indicated in the electrocardiogram recording, it is markedby various imaging or localization means. An ablation catheter with oneor more electrodes can then transmit electrical energy to the tissueadjacent the electrode to create a lesion in the tissue. One or moresuitably positioned lesions will typically create a region of necrotictissue which serves to disable the propagation of the aberrant impulse.Ablation is carried out by applying energy to the catheter electrodes.The ablation energy can be, for example, RF, DC, ultrasound, microwave,cryogenic or laser radiation. The same catheter may be used both formapping and ablation, or two or more different catheters may beemployed.

Conventional atrial ablation catheters may be employed to create thedesired disturbance of an inter-atrial conduction pathway, includingsingle point electrode catheters, balloon electrode catheters, and loopelectrode catheters. The inventors have found that a catheter includinga braided conductive member, such as a wire mesh, is particularly suitedfor treatment of inter-atrial fibrillation by ablation of one or more ofthe inter-atrial conduction paths and also is indicated for treatment ofaccessory path arrythmias by the ablation of the vicinity of thecoronary sinus ostium. The mesh may have a slender configurationcompatible with percutaneous transport and an expanded deployedconfiguration suitable for contacting the region of undesired conductionand, when energized, will apply a suitable lesion to block propagationof the undesired electrical signals such as between the left and rightatria in connection with the treatment of atrial fibrillation.

System Overview

Reference is now made to FIG. 1, which figure illustrates an overview ofa mapping and ablation catheter system in accordance with the presentinvention. The system includes a catheter 10 having a shaft portion 12,a control handle 14, and a connector portion 16. A controller 8 isconnected to connector portion 16 via cable 6. Ablation energy generator4 may be connected to controller 8 via cable 3. A recording device 2 maybe connected to controller 8 via cable 1. When used in an ablationapplication, controller 8 is used to control ablation energy provided byablation energy generator 4 to catheter 10. When used in a mappingapplication, controller 8 is used to process signals coming fromcatheter 10 and to provide these signals to recording device 2. Althoughillustrated as separate devices, recording device 2, ablation energygenerator 4, and controller 8 could be incorporated into a singledevice. In one embodiment, controller 8 may be a QUADRAPULSE RFCONTROLLER™ device available from CR Bard, Inc., Murray Hill, N.J.

In this description, various aspects and features of the presentinvention will be described. The various features of the invention arediscussed separately for clarity. One skilled in the art will appreciatethat the features may be selectively combined in a device depending uponthe particular application. Furthermore, any of the various features maybe incorporated in a catheter and associated method of use for eithermapping or ablation procedures.

Catheter Overview

Reference is now made to FIGS. 2-7, which figures illustrate oneembodiment of the present invention. The present invention generallyincludes a catheter and method of its use for mapping and ablation inelectrophysiology procedures. Catheter 10 includes a shaft portion 12, acontrol handle 14, and a connector portion 16. When used in mappingapplications, connector portion 16 is used to allow signal wires runningfrom the electrodes at the distal portion of the catheter to beconnected to a device for processing the electrical signals, such as arecording device.

Catheter 10 may be a steerable device. FIG. 2 illustrates the distal tipportion 18 being deflected by the mechanism contained within controlhandle 14. Control handle 14 may include a rotatable thumb wheel whichcan be used by a user to deflect the distal end of the catheter. Thethumb wheel (or any other suitable actuating device) is connected to oneor more pull wires which extend through shaft portion 12 and areconnected to the distal end 18 of the catheter at an off-axis location,whereby tension applied to one or more of the pull wires causes thedistal portion of the catheter to curve in a predetermined direction ordirections. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777, whichare hereby incorporated by reference, illustrate various embodiments ofcontrol handle 14 that may be used for steering catheter 10.

Shaft portion 12 includes a distal tip portion 18, a first stop 20 andan inner member 22 connected to the first stop portion 20. Inner member22 may be a tubular member. Concentrically disposed about inner member22 is a first sheath 24 and a second sheath 26. Also concentricallydisposed about inner member 22 is a braided conductive member 28anchored at respective ends 30 and 32 to the first sheath 24 and thesecond sheath 26, respectively.

In operation, advancing the second sheath 26 distally over inner member22 causes the first sheath 24 to contact stop 20. Further distaladvancement of the second sheath 26 over inner member 22 causes thebraided conductive member 28 to expand radially to assume variousdiameters and/or a conical shape. FIGS. 1 and 4 illustrate braidedconductive member 28 in an unexpanded (collapsed or “undeployed”)configuration. FIGS. 3, 5, and 6 illustrate braided conductive member 28in a partially expanded condition. FIG. 2 illustrates braided conductivemember 28 radially expanded (“deployed”) to form a disk. Furthermovement of inner member 22, first sheath 24, and second sheath 26 withrespect to each other may be used to form the conical shape previouslyreferred to and in particular the braided conductive member may beformed into a cone having a distal-facing tissue contacting and/or acone having a proximal-facing tissue contact ring.

Alternatively, braided conductive member 28 can be radially expanded bymoving inner member 22 proximally with respect to the second sheath 26.

As another alternative, inner member 22 and distal tip portion 18 may bethe same shaft and stop 20 may be removed. In this configuration, sheath24 moves over the shaft in response to, for example, a mandrel insideshaft 22 and attached to sheath 24 in the manner described, for example,in U.S. Pat. No. 6,178,354, which is incorporated herein by reference.

As illustrated particularly in FIGS. 4 and 5 a third sheath 33 may beprovided. The third sheath serves to protect shaft portion 12 and inparticular braided conductive member 28 during manipulation through thepatient's vasculature. In addition, the third sheath 33 shields braidedconductive member 28 from the patient's tissue in the event ablationenergy is prematurely delivered to the braided conductive member 28.

The respective sheaths 24, 26, and 33 can be advanced and retracted overthe inner member 22, which may be a tubular member, in many differentmanners. Control handle 14 may be used. U.S. Pat. Nos. 5,383,852,5,462,527, and 5,611,777 illustrate examples of control handles that cancontrol sheaths 24, 26, and 33. As described in these incorporated byreference patents, control handle 14 may include a slide actuator whichis axially displaceable relative to the handle. The slide actuator maybe connected to one of the sheaths, for example, the second sheath 26 tocontrol the movement of the sheath 26 relative to inner member 22, todrive braided conductive member 28 between respective collapsed anddeployed positions, as previously described. Control handle 14 may alsoinclude a second slide actuator or other mechanism coupled to theretractable outer sheath 32 to selectively retract the sheath in aproximal direction with respect to the inner member 22.

Braided conductive member 28 is, in one embodiment of the invention, aplurality of interlaced, electrically conductive filaments 34. Braidedconductive member 28 may be a wire mesh. The filaments are flexible andcapable of being expanded radially outwardly from inner member 22. Thefilaments 34 are preferably formed of metallic elements havingrelatively small cross sectional diameters, such that the filaments canbe expanded radially outwardly. The filaments may be round, having adimension on the order of about 0.001-0.030 inches in diameter.Alternatively, the filaments may be flat, having a thickness on theorder of about 0.001-0.030 inches, and a width on the order of about0.001-0.030 inches. The filaments may be formed of Nitinol type wire.Alternatively, the filaments may include non metallic elements wovenwith metallic elements, with the non metallic elements providing supportto or separation of the metallic elements. A multiplicity of individualfilaments 34 may be provided in braided conductive member 28, forexample up to 300 or more filaments.

Each of the filaments 34 can be electrically isolated from each other byan insulation coating. This insulation coating may be, for example, apolyamide type material. A portion of the insulation on the outercircumferential surface 60 of braided conductive member 28 is removed.This allows each of the filaments 34 to form an isolated electrode, notan electrical contact with any other filament, that may be used formapping and ablation. Alternatively, specific filaments may be permittedto contact each other to form a preselected grouping.

Each of the filaments 34 is helically wound under compression aboutinner member 22. As a result of this helical construction, upon radialexpansion of braided conductive member 28, the portions of filaments 34that have had the insulation stripped away do not contact adjacentfilaments and thus, each filament 34 remains electrically isolated fromevery other filament. FIGS. 6 and 6A illustrate how the insulation maybe removed from individual filaments 34 while still providing isolationbetween and among the filaments. As illustrated in FIG. 6A, regions 50illustrate regions, on the outer circumferential surface 60 of braidedconductive member 28, where the insulation has been removed fromindividual filaments 34. In one embodiment of the invention, theinsulation may be removed from up to one half of the outer facingcircumference of each of the individual filaments 34 while stillretaining electrical isolation between each of the filaments 34.

The insulation on each of the filaments 34 that comprise braidedconductive member 28 may be removed about the outer circumferentialsurface 60 of braided conductive member 28 in various ways. For example,one or more circumferential bands may be created along the length ofbraided conductive member 28. Alternatively, individual sectors orquadrants only may have their insulation removed about the circumferenceof braided conductive member 28. Alternatively, only selected filaments34 within braided conductive member 28 may have their circumferentiallyfacing insulation removed. Thus, an almost limitless number ofconfigurations of insulation removal about the outer circumferentialsurface 60 of braided conductive member 28 can be provided dependingupon the mapping and ablation characteristics and techniques that aclinician desires.

The insulation on each of the filaments 34 may be removed at the outercircumferential surface 60 of braided conductive member 28 in a varietyof ways as long as the insulation is maintained between filaments 34 sothat filaments 34 remain electrically isolated from each other.

The insulation can be removed from the filaments 34 in a variety of waysto create the stripped portions 50 on braided conductive member 28. Forexample, mechanical means such as abration or scraping may be used. Inaddition, a water jet, chemical means, or thermal radiation means may beused to remove the insulation.

In one example of insulation removal, braided conductive member 28 maybe rotated about inner member 22, and a thermal radiation source such asa laser may be used to direct radiation at a particular point along thelength of braided conductive member 28. As the braided conductive member28 is rotated and the thermal radiation source generates heat, theinsulation is burned off the particular region.

Insulation removal may also be accomplished by masking selected portionsof braided conductive member 28. A mask, such as a metal tube may beplaced over braided conducive member 28. Alternatively, braidedconductive member 28 may be wrapped in foil or covered with some type ofphotoresist. The mask is then removed in the areas in which insulationremoval is desired by, for example, cutting away the mask, slicing thefoil, or removing the photoresist. Alternatively, a mask can be providedthat has a predetermined insulation removal pattern. For example, ametal tube having cutouts that, when the metal tube is placed overbraided conductive member 28, exposes areas where insulation is to beremoved.

FIG. 7 illustrates how thermal radiation 52 may be applied to the outercircumferential surface 56 of a respective filament 34 that defines theouter circumferential surface 60 of braided conductive member 28. Asthermal radiation 52 is applied, the insulation 54 is burned off orremoved from the outer circumference 56 of wire 34 to create a region 58about the circumference 56 of filament 34 that has no insulation.

The insulation 54 can also be removed in a preferential manner so that aparticular portion of the circumferential surface 56 of a filament 34 isexposed. Thus, when braided conductive. member 28 is radially expanded,the stripped portions of filaments may preferentially face the intendeddirection of mapping or ablation.

Although removal of insulation from filaments 34 in the vicinity of theouter circumferential surface 60 has been discussed in detail above,insulation can be removed from one or more filaments 34 that comprisebraided conductive member 28 anywhere along the length of the filament.For example, as illustrated in U.S. Pat. No. 6,315,778, which isincorporated herein by reference, braided conductive member 28 may beexpanded so that it forms a distal-facing ring. In this configuration,the insulation may be removed from filaments 34 in the vicinity of thedistal-facing ring. In another embodiment, braided conductive member 28may be expanded so that it forms a proximal-facing ring and insulationmay be removed in the vicinity of the proximal-facing ring. Insulationmay be selectively removed to define mapping and/or ablation filamentsanywhere on the proximal side, distal side, or circumferential surfaceof braided conductive member 28 when in its expanded or deployedconfiguration.

With the insulation removed from the portions of filaments 34 on theouter circumferential surface 60 of braided conductive member 28, aplurality of individual mapping and ablation channels can be created. Awire runs from each of the filaments 34 within catheter shaft 12 andcontrol handle 14 to connector portion 16. A multiplexer or switch boxmay be connected to the conductors so that each filament 34 may becontrolled individually. This function may be incorporated intocontroller 8. A number of filaments 34 may be grouped together formapping and ablation. Alternatively, each individual filament 34 can beused as a separate mapping channel for mapping individual electricalactivity within a blood vessel at a single point. Using a switch box ormultiplexer to configure the signals being received by filaments 34 orablation energy sent to filaments 34 results in an infinite number ofpossible combinations of filaments for detecting electrical activityduring mapping procedures and for applying energy during an ablationprocedure.

The ability to individually define a filament 34 as a mapping orablation channel may be combined with selective insulation removal froma filament to create a wide variety of mapping/ablation configurations.For example, insulation may be removed from a number of filaments tocreate an ablative ring around the outer circumferential surface ofbraided conductive member 28 and insulation may be selectively removedfrom another filament on the proximal and/or distal side of a filamentthat is inside the ablative ring but electrically insulated from thefilaments forming the ablative ring to define a mapping channel. Thiscan allow a user to ablate tissue in contact with the ring and thencheck for electrical activity inside the ring using the filament definedas the mapping channel before, during, and/or after an ablationoperation. In another embodiment, the ablative ring can be formed insidea mapping channel to allow checking electrical activity outside theablative ring. These configurations can also be combined to provide anouter mapping channel or channels outside the ablative ring, an ablationring (or element), and an inner mapping channel or channels inside theablation ring or element concentrically arranged about the cathetershaft.

In accordance with the invention, a single catheter that provides bothmapping and ablation functions can reduce the number of catheter changesneeded during an electrophysiology procedure and can allow feedbacksimultaneously with or shortly after ablation to determine theeffectiveness of an ablation operation.

By controlling the amount of insulation that is removed from thefilaments 34 that comprise braided conductive member 28, the surfacearea of the braid that is in contact with a blood vessel wall can alsobe controlled. This in turn will allow control of the impedancepresented to an ablation energy generator, for example, generator 4. Inaddition, selectively removing the insulation can provide apredetermined or controllable profile of the ablation energy deliveredto the tissue.

The above description illustrates how insulation may be removed from thefilaments 34. Alternatively, the same features and advantages can beachieved by adding insulation to filaments 34. For example, filaments 34may be bare wire and insulation can be added to them.

Individual control of the electrical signals received from filaments 34allows catheter 10 to be used for bipolar (differential or betweenfilament) type mapping as well as unipolar (one filament with respect toa reference) type mapping.

Catheter 10 may also have, as illustrated in FIGS. 2 and 3, a referenceelectrode 13 mounted on shaft 12 so that reference electrode 13 islocated outside the heart during unipolar mapping operations.

Radiopaque markers can also be provided for use in electrode orientationand identification.

One skilled in the art will appreciate all of the insulation can beremoved from filaments 34 to create a large ablation electrode.

Although a complete catheter steerable structure has been illustrated,the invention can also be adapted so that inner tubular member 22 is acatheter shaft, guide wire, or a hollow tubular structure forintroduction of saline, contrast media, heparin or other medicines, orintroduction of guidewires, or the like.

Temperature Sensing

A temperature sensor or sensors, such as, but not limited to, one ormore thermocouples may be attached to braided conductive member 28 fortemperature sensing during ablation procedures. A plurality ofthermocouples may also be woven into the braided conductive member 28.An individual temperature sensor could be provided for each of thefilaments 34 that comprise braided conductive member 28. Alternatively,braided conductive member 28 can be constructed of one or moretemperature sensors themselves.

FIG. 8 illustrates braided conductive member 28 in its fully expanded ordeployed configuration. Braided conductive member 28 forms a disk whenfilly expanded. In the embodiment illustrated in FIG. 8, there aresixteen filaments 34 that make up braided conductive member 28.

Temperature monitoring or control can be incorporated into braidedconductive member 28, for example, by placing temperature sensors (suchas thermocouples, thermistors, etc.) on the expanded braided conductivemember 28 such that they are located on the distally facing ablativering formed when braided conductive member 28 is in its fully expandedconfiguration. “Temperature monitoring” refers to temperature reportingand display for physician interaction. “Temperature control” refers tothe capability of adding an algorithm in a feedback loop to titratepower based on temperature readings from the temperature sensorsdisposed on braided conductive member 28. Temperature sensors canprovide a means of temperature control provided the segment of theablative ring associated with each sensor is independently controllable(e.g., electrically isolated from other regions of the mesh). Forexample, control can be achieved by dividing the ablative structure intoelectrically independent sectors, each with a temperature sensor, oralternatively, each with a mechanism to measure impedance in order tofacilitate power titration. The ablative structure may be divided intoelectrically independent sectors so as to provide zone control. Theprovision of such sectors can be used to provide power control tovarious sections of braided conductive member 28.

Reference is now made to FIGS. 8-9. As illustrated in FIG. 8, fourtemperature sensors 70 are provided on braided conductive member 28. Asnoted previously, since the individual filaments 34 (34 a-34 p in FIG.8) in braided conductive member 28 are insulated from each other, anumber of independent sectors may be provided. A sector may include oneor more filaments 34. During ablation procedures, energy can be appliedto one or more of the filaments 34 in any combination desired dependingupon the goals of the ablation procedure. A temperature sensor could beprovided on each filament 34 of braided conductive member 28 or sharedamong one or more filaments. In mapping applications, one or more of thefilaments 34 can be grouped together for purposes of measuringelectrical activity. These sectoring functions can be provided incontroller 8.

FIG. 10 illustrates a side view of braided conductive member 28including temperature sensors 70. As shown in FIG. 10, temperaturesensors 70 emerge from four holes 72. Each hole 72 is disposed in onequadrant of anchor 74. The temperature sensors 70 are bonded to theoutside edge 76 of braided conductive member 28. Temperature sensors 70may be isolated by a small piece of polyimide tubing 73 around them andthen bonded in place to the filaments. The temperature sensors 70 may bewoven and twisted into braided conductive member 28 or they can bebonded in a side-by-side or parallel manner with the filaments 34.

There are several methods of implementing electrically independentsectors. In one embodiment, the wires are preferably stripped of theirinsulative coating in the region forming the ablative ring (whenexpanded). However, sufficient insulation may be left on the wires inorder to prevent interconnection when in the expanded state.Alternatively, adjacent mesh wires can be permitted to touch in theirstripped region, but can be separated into groups by fully insulated(unstripped) wires imposed, for example, every 3 or 5 wires apart (thenumber of wires does not limit this invention), thus forming sectors ofindependently controllable zones. Each zone can have its own temperaturesensor. The wires can be “bundled” (or independently attached) toindependent outputs of an ablation energy generator. RF energy can thenbe titrated in its application to each zone by switching power on andoff (and applying power to other zones during the ‘off period’) or bymodulating voltage or current to the zone (in the case of independentcontrollers). In either case, the temperature inputs from thetemperature sensors can be used in a standard feedback algorithm tocontrol the power delivery.

Alternatively, as illustrated in FIG. 10A, braided conductive member 28may be used to support a ribbon-like structure which is separated intodiscrete sectors. As shown in FIG. 10A, the ribbon-like structure 81 maybe, for example, a pleated copper flat wire that, as braided conductivemember 28 expands, unfolds into an annular ring. Each of the wires 83a-83 d lie in the same plane. Although four wires are illustrated inFIG. 10A, structure 81 may include any number of wires depending uponthe application and desired performance. Each of wires 83 a-83 d isinsulated. Insulation may then be removed from each wire to createdifferent sectors 85 a-85 d. Alternatively, each of wires 83 a-83 d maybe uninsulated and insulation may be added to create different sectors.The different sectors may provide an ablative zone comprised ofindependently controllable wires 83 a-83 d. Temperature sensors 70 maybe mounted on the individual wires, and filaments 34 may be connected torespective wires 83 a-83 d to provide independent control of energy toeach individual sector. One skilled in the art will appreciate that eachof wires 83 a-83 d can have multiple sectors formed by removinginsulation in various locations and that numerous combinations ofsectors 85 a-85 d and wires 83 a-83 d forming ribbon-like structure 81can be obtained.

Further, according to the invention, some of sectors 85 a-85 d or wires83 a-83 d may be used for mapping or electrical measurement, while otherof these sectors 85 a-85 d or wires 83 a-83 d may be used for ablation.The mapping and ablations sectors and/or wires may be activatedindependently, and may be activated concurrently, if desired. Oneapplication of dedicating some sectors and/or wires for mapping andothers for ablation is that a lesion may be formed and the quality ofthe lesion may be measured using a single braided conductive member 28.This can avoid the need to change catheters during a procedure. Thus, asingle catheter may be used for both mapping and ablation.

The quality of a lesion may be determined by a measurement of theimpedance of the ablated tissue or by a measurement of the electricalsignal strength at the ablated tissue. Impedance of the tissue may bedetermined by measuring the resistance between any two sectors 85 a-85 dor wires 83 a-83 d dedicated to mapping based on a known input voltageor current. Ablated tissue has a higher impedance than healthy tissue;thus, a higher impedance value is indicative of a higher degree ofablation. Electrical signal strength may be a unipolar measurement basedon a single sector 85 a-85 d or wire 83 a-83 d. If a measurement of asignal is detected in healthy tissue, the signal will have a higheramplitude than a signal that is detected in ablated tissue. Accordingly,a determination may be made as to the health of the tissue, or qualityof the lesion.

Measurement of the impedance of the ablated tissue or measurement of theelectrical signal strength at the ablated tissue, described above, mayalso be performed with other embodiments of the catheter 10 describedherein. For example, in the embodiment of FIG. 8., one or more of thesixteen filaments 34 may be used to measure the signal strength of theablated tissue. For example, a single filament 34 that is isolated fromthe other filaments or a group of electrically connected filaments maybe used. Multiple measurements of the signal strength may be taken indifferent regions of the braided conductive member 28 and compared toassess the signal strength in different regions or quadrants of thebraided conductive member 28. Similarly, any two of the sixteenfilaments 34 of FIG. 8 or any two groups of electrically connectedfilaments, may be used to measure the signal strength of the ablatedtissue to measure the impedance between each of the two filaments 34 orgroups of filaments.

Either of the impedance measurement or the signal strength measurementmay be performed independently by various sectors 85 a-85 d or wires 83a-83 d of the braided conductive member. This allows an assessment oflesion quality to be performed for different regions of a lesion,corresponding to different quadrants of the braided conductive member28.

Steering

Reference is now made to FIGS. 11-13 which illustrate aspects of thesteering capabilities of the present invention. As illustrated in FIGS.1-2, catheter 10 is capable of being steered using control handle 14. Inparticular, FIG. 2 illustrates steering where the steering pivot orknuckle is disposed on catheter shaft 12 in a region that is distal tothe braided conductive member 28.

FIG. 11 illustrates catheter 10 wherein the pivot point or steeringknuckle is disposed proximal to braided conductive member 28.

FIG. 12 illustrates catheter 10 having the capability of providingsteering knuckles both proximal and distal to braided conductive member28.

FIGS. 2 and 11-12 illustrate two dimensional or single plane typesteering. The catheter of the present invention can also be used inconnection with a three dimensional steering mechanism. For example,using the control handle in the incorporated by reference '852 patent,the catheter can be manipulated into a three-dimensional “lasso-like”shape, particularly at the distal end of the catheter. As shown in FIG.13, the catheter can have a primary curve 80 in one plane and then asecond curve 82 in another plane at an angle to the first plane. Withthis configuration, the catheter can provide increased access todifficult to reach anatomical structures. For example, a target site fora mapping or ablation operation may be internal to a blood vessel. Thus,the increased steering capability can allow easier access into thetarget blood vessel. In addition, the additional dimension of steeringcan allow for better placement of braided conductive member 28 during anablation or mapping procedure. Catheter 10 can be inserted into a siteusing the steering capabilities provided by primary curve 80.Thereafter, using the secondary curve 82, braided conductive member 28can be tilted into another plane for better orientation or contact withthe target site.

Conductive Member Configurations And Materials

Reference is now made to FIGS. 14-17 which figures illustrate otherconfigurations of braided conductive member 28. As has been describedabove and will be described in more detail, braided conductive member 28can include from one to 300 or more filaments. The filaments may varyfrom very fine wires having small diameters or cross-sectional areas tolarge wires having relatively large diameters or cross-sectional areas.

FIG. 14 illustrates the use of more than one braided conductive member28 at the distal end of catheter 10. As shown in FIG. 14, three braidedconductive members 28A, 28B, and 28C are provided at the distal end ofcatheter 10. Braided conductive members 28A, 28B, and 28C may be, intheir expanded conditions, the same size or different sizes. Each of thebraided conductive members 28A, 28B, and 28C can be expanded orcontracted independently in the manner illustrated in FIGS. 1-4 viaindependent control shafts 26A, 26B, and 26C. The use of multiplebraided conductive members provides several advantages. Rather thanhaving to estimate or guess as to the size of the blood vessel prior tostarting a mapping or ablation procedure, if braided conductive members28A, 28B, and 28C are of different expanded diameters, than sizing canbe done in vivo during a procedure. In addition, one of the braidedconductive members can be used for ablation and another of the braidedconductive members can be used for mapping. This allows for quicklychecking the effectiveness of an ablation procedure.

Reference is now made to FIG. 15A and 15B, which figures illustrateother shapes of braided conductive member 28. As described up to thispoint, braided conductive member 28 is generally symmetrical and coaxialwith respect to catheter shaft 12. However, certain anatomicalstructures may have complex three-dimensional shapes that are not easilyapproximated by a geometrically symmetrical mapping or ablationstructure. One example of this type of structure occurs at the CSostium. To successfully contact these types of anatomical structures,braided conductive member 28 can be “preformed” to a close approximationof that anatomy, and yet still be flexible enough to adapt to variationsfound in specific patients. Alternatively, braided conductive member 28can be “preformed” to a close approximation of that anatomy, and be ofsufficient strength (as by choice of materials, configuration, etc.) toforce the tissue to conform to variations found in specific patients.For example, FIG. 15A illustrates braided conductive member 28 disposedabout shaft 12 in an off-center or non-concentric manner. In addition,braided conductive member 28 may be constructed so that the parameter ofthe braided conductive member 28 in its expanded configuration has anon-circular edge so as to improve tissue contact around the parameterof the braided conductive member. FIG. 15B illustrates an example ofthis type of configuration where the braided conductive member 28 isboth off center or non concentric with respect to catheter shaft 12 andalso, in its deployed or expanded configuration, has an asymmetricshape. The eccentricity of braided conductive member 28 with respect tothe shaft and the asymmetric deployed configurations can be produced byproviding additional structural supports in braided conductive member28, for example, such as by adding nitinol, ribbon wire, and so on. Inaddition, varying the winding pitch or individual filament size orplacement or deforming selective filaments in braided conductive member28 or any other means known to those skilled in the art may be used.

FIGS. 16A-16C illustrate another configuration of braided conductivemember 28 and catheter 10. As illustrated in FIGS. 16A-16C, the distaltip section of catheter 10 has been removed and braided conductivemember 28 is disposed at the distal end of catheter 10. One end ofbraided conductive member 28 is anchored to catheter shaft 12 using ananchor band 90 that clamps the end 32 of braided conductive member 28 tocatheter shaft 12. The other end of braided conductive member 28 isclamped to an activating shaft such as shaft 26 using another anchorband 92. FIG. 16A illustrates braided conductive member 28 in itsundeployed configuration. As shaft 22 is moved distally, braidedconductive member 28 emerges or everts from shaft 12. As shown in FIG.16B, braided conductive member 28 has reached its fully deployeddiameter and an annular tissue contact zone 29 can be placed against anostium or other anatomical structure. As illustrated in FIG. 16C,further distal movement of shaft 22 can be used to create a concentriclocating region 94 that can help to provide for concentric placementwithin an ostium of a pulmonary vein, for example. Concentric locatingregion 94 may be formed by selective variations in the winding densityof filaments 34 in braided conductive member 28, preferentialpredeformation of the filaments, additional eversion of braidedconductive member 28 from shaft 12, or by other means known to thoseskilled in the art.

Reference is now made to FIG. 17, which figure illustrates a furtherembodiment of braided conductive member 28. As illustrated in FIG. 17,braided conductive member 28 is composed of one or several large wires96 rather than a multiplicity of smaller diameter wires. The wire orwires can be moved between the expanded and unexpanded positions in thesame manner as illustrated in FIG. 1. In addition, a region 98 may beprovided in which the insulation has been removed for mapping orablation procedures. The single wire or “corkscrew” configurationprovides several advantages. First, the wire or wires do not cross eachother and therefore there is only a single winding direction requiredfor manufacture. In addition, the risk of thrombogenicity may be reducedbecause there is a smaller area of the blood vessel being blocked. Inaddition, the connections between the ends of the large wire and thecontrol shafts may be simplified.

The catheter 10 of the present invention can be coated with a number ofcoatings that can enhance the operating properties of braided conductivemember 28. The coatings can be applied by any of a number of techniquesand the coatings may include a wide range of polymers and othermaterials.

Braided conductive member 28 can be coated to reduce its coefficient offriction, thus reducing the possibility of thrombi adhesion to thebraided conductive member as well as the possibility of vascular oratrial damage. These coatings can be combined with the insulation on thefilaments that make up braided conductive member 28, these coatings canbe included in the insulation itself, or the coatings can be applied ontop of the insulation. Examples of coating materials that can be used toimprove the lubricity of the catheter include PD slick available fromPhelps Dodge Corporation, Ag, Tin, BN. These materials can be applied byan ion beam assisted deposition (“IBAD”) technique developed by, forexample, Amp Corporation.

Braided conductive member 28 can also be coated to increase or decreaseits thermal conduction which can improve the safety or efficacy of thebraided conductive member 28. This may be achieved by incorporatingthermally conductive elements into the electrical insulation of thefilaments that make up braided conductive member 28 or as an addedcoating to the assembly. Alternatively, thermally insulating elementsmay be incorporated into the electrical insulation of the filaments thatmake up braided conductive member 28 or added as a coating to theassembly. Polymer mixing, IBAD, or similar technology could be used toadd Ag, Pt, Pd, Au, Ir, Cobalt, and others into the insulation or tocoat braided conductive member 28.

Radiopaque coatings or markers can also be used to provide a referencepoint for orientation of braided conductive member 28 when viewed duringfluoroscopic imaging. The materials that provide radiopacity including,for example, Au, Pt, Ir, and other known to those skilled in the art.These materials may be incorporated and used as coatings as describedabove.

Antithrombogenic coatings, such as heparin and BH, can also be appliedto braided conductive member 28 to reduce thrombogenicity to preventblood aggregation on braided conductive member 28. These coatings can beapplied by dipping or spraying, for example.

As noted above, the filament 34 of braided conductive member 28 may beconstructed of metal wire materials. These materials may be, forexample, MP35N, nitinol, or stainless steel. Filaments 34 may also becomposites of these materials in combination with a core of anothermaterial such as silver or platinum. The combination of a highlyconductive electrical core material with another material forming theshell of the wire allows the mechanical properties of the shell materialto be combined with the electrical conductivity of the core material toachieve better and/or selectable performance. The choice and percentageof core material used in combination with the choice and percentage ofshell material used can be selected based on the desired performancecharacteristics and mechanical/electrical properties desired for aparticular application.

Irrigation

It is known that for a given electrode side and tissue contact area, thesize of a lesion created by radiofrequency (RF) energy is a function ofthe RF power level and the exposure time. At higher powers, however, theexposure time can be limited by an increase in impedance that occurswhen the temperature at the electrode-tissue interface approaches 100°C. One way of maintaining the temperature less than or equal to thislimit is to irrigate the ablation electrode with saline to provideconvective cooling so as to control the electrode-tissue interfacetemperature and thereby prevent an increase in impedance. Accordingly,irrigation of braided conductive member 28 and the tissue site at whicha lesion is to be created can be provided in the present invention. FIG.18 illustrates the use of an irrigation manifold within braidedconductive member 28. An irrigation manifold 100 is disposed along shaft22 inside braided conductive member 28. Irrigation manifold 100 may beone or more polyimid tubes. Within braided conductive member 28, theirrigation manifold splits into a number of smaller tubes 102 that arewoven into braided conductive member 28 along a respective filament 34.A series of holes 104 may be provided in each of the tubes 102. Theseholes can be oriented in any number of ways to target a specific site orportion of braided conductive member 28 for irrigation. Irrigationmanifold 100 runs through catheter shaft 12 and may be connected to anirrigation delivery device outside the patient used to inject anirrigation fluid, such as saline, for example, such as during anablation procedure.

The irrigation system can also be used to deliver a contrast fluid forverifying location or changes in vessel diameter. For example, acontrast medium may be perfused prior to ablation and then after anablation procedure to verify that there have been no changes in theblood vessel diameter. The contrast medium can also be used duringmapping procedures to verify placement of braided conductive member 28.In either ablation or mapping procedures, antithrombogenic fluids, suchas heparin can also be perfused to reduce thrombogenicity.

FIGS. 19 and 19A illustrate another way of providingperfusion/irrigation in catheter 10. As illustrated in FIGS. 19 and 19A,the filaments 34 that comprise braided conductive member 28 are composedof a composite wire 110. The composite wire 110 includes an electricallyconductive wire 112 that is used for delivering ablation energy in anablation procedure or for detecting electrical activity during a mappingprocedure. Electrical wire 112 is contained within a lumen 114 that alsocontains a perfusion lumen 116. Perfusion lumen 116 is used to deliverirrigation fluid or a contrast fluid as described in connection withFIG. 18. Once braided conductive member 28 has been constructed withcomposite wire 110, the insulation 118 surrounding wire filament 112 canbe stripped away to form an electrode surface. Holes can then beprovided into perfusion lumen 116 to then allow perfusion at targetedsites along the electrode surface. As with the embodiment illustrated inFIG. 18, the perfusion lumens can be connected together to form amanifold which manifold can then be connected to, for example, perfusiontube 120 and connected to a fluid delivery device.

Shrouds

The use of a shroud or shrouds to cover at least a portion of braidedconductive member 28 can be beneficial in several ways. The shroud canadd protection to braided conductive member 28 during insertion andremoval of catheter 10. A shroud can also be used to form or shapebraided conductive member 28 when in its deployed state. Shrouds mayalso reduce the risk of thrombi formation on braided conductive member28 by reducing the area of filament and the number of filament crossingsexposed to blood contact. This can be particularly beneficial at theends 30 and 32 of braided conductive member 28. The density of filamentsat ends 30 and 32 is greatest and the ends can therefore be prone toblood aggregation. The shrouds can be composed of latex balloon materialor any material that would be resistant to thrombi formation durableenough to survive insertion through an introducer system, and would notreduce the mobility of braided conductive member 28. The shrouds canalso be composed of an RF transparent material that would allow RFenergy to pass through the shroud. If an RF transparent material isused, complete encapsulation of braided conductive member 28 ispossible.

A shroud or shrouds may also be useful when irrigation or perfusion isused, since the shrouds can act to direct irrigation or contrast fluidto a target region.

FIGS. 20A-20E illustrate various examples of shrouds that may be used inthe present invention. FIG. 20A illustrates shrouds 130 and 132 disposedover end regions 30 and 32, respectively, of braided conductive member28. This configuration can be useful in preventing coagulation of bloodat the ends of braided conductive member 28. FIG. 20B illustratesshrouds 130 and 132 used in conjunction with an internal shroud 134contained inside braided conductive member 28. In addition to preventingblood coagulation in regions 30 and 32, the embodiment illustrated inFIG. 20B also prevents blood from entering braided conductive member 28.

FIG. 20C illustrates shrouds 130 and 132 being used to direct andirrigation fluid or contrast medium along the circumferential edge ofbraided conductive member 28. In the embodiment illustrated in FIG. 20C,perfusion can be provided as illustrated in FIGS. 18 and 19.

FIG. 20D illustrates the use of an external shroud that covers braidedconductive member 28. Shroud 136 completely encases braided conductivemember 28 and thereby eliminates blood contact with braided conductivemember 28. Shroud 136 may be constructed of a flexible yetablation-energy transparent material so that, when used in an ablationprocedure, braided conductive member 28 can still deliver energy to atargeted ablation site.

FIG. 20E also illustrates an external shroud 137 encasing braidedconductive member 28. Shroud 137 may also be constructed of a flexibleyet ablation-energy transparent material. Openings 139 may be providedin shroud 137 to allow the portions of braided conductive member 28 thatare exposed by the opening to come into contact with tissue. Openings139 may be elliptical, circular, circumferential, etc.

Guiding Sheaths

There may be times during ablation or mapping procedures when catheter10 is passing through difficult or tortuous vasculature. During thesetimes, it may be helpful to have a guiding sheath through which to passcatheter 10 so as to allow easier passage through the patient'svasculature.

FIG. 21 illustrates one example of a guiding sheath that may be used inconnection with catheter 10. As illustrated in FIG. 21, the guidingsheath 140 includes a longitudinal member 142. Longitudinal member 142may be constructed of a material rigid enough to be pushed next tocatheter shaft 12 as the catheter is threaded through the vasculature.In one example, longitudinal member 142 may be stainless steel.Longitudinal member 142 is attached to a sheath 144 disposed at thedistal end 146 of longitudinal member 142. The split sheath 144 may haveone or more predetermined curves 148 that are compatible with the shapesof particular blood vessels (arteries or veins) that catheter 10 needsto pass through. Split sheath 144 may extend proximally alonglongitudinal member 142. For example, sheath 144 and longitudinal member142 may be bonded together for a length of up to 20 or 30 centimeters toallow easier passage through the patient's blood vessels. Sheath 144includes a predetermined region 162 that extends longitudinally alongsheath 144. Region 162 may be, for example, a seam, that allows sheath144 to be split open so that the guiding sheath 140 can be pulled backand peeled off catheter shaft 12 in order to remove the sheath.

In another embodiment, longitudinal member 142 may be a hypotube or thelike having an opening 152 at distal end 146 that communicates with theinterior of sheath 144. In this embodiment, longitudinal member 142 canbe used to inject irrigation fluid such as saline or a contrast mediumfor purposes of cooling, flushing, or visualization.

Localization Localization refers to a number of techniques whereby thelocation of catheter 1 in a patient can be determined. Apparatus andmethods for localization can be incorporated into catheter 10.

An electromagnetic sensor, used for localization, may be fixed withinthe shaft of the catheter 10 using any suitable mechanism, such as glueor solder. The electromagnetic sensor generates signals indicative ofthe location of the electromagnetic sensor. A wire electrically connectsthe electromagnetic sensor to the controller 8, allowing the generatedsignals to be transmitted to the controller 8 for processing.

In addition to the electromagnetic sensor fixed to the catheter, asecond electromagnetic sensor is provided that is fixed relative to thepatient. The second electromagnetic sensor is attached, for example, tothe patient's body, and serves as a reference sensor. A magnetic fieldis also provided, which is exposed to the electromagnetic sensors. Coilswithin each electromagnetic sensor generate electrical currents whenexposed to the magnetic field. The electrical current generated by thecoils of each sensor corresponds to a position of each sensor within themagnetic field. Signals generated by the reference electromagneticsensor and electromagnetic sensor fixed to the catheter are analyzed bythe controller 8 to ascertain a precise location of electromagneticsensor fixed to the catheter 10.

Further, the signals can be used to generate a contour map of the heart.The map may be generated by contacting the catheter 10 with the hearttissue at a number of locations along the heart wall. At each location,the electric signals generated by the electromagnetic sensors aretransmitted to the controller 8, or to another processor, to determineand record a location of the catheter 10. The contour map is generatedby compiling the location information for each point of contact. Thismap may be correlated with heart signal data, measured by one or moreelectrodes on the catheter, for each location to generate a map of boththe shape and electrical activity of the heart. Signals generated by theelectromagnetic sensors may also be analyzed to determine a displacementof the catheter 10 caused by heartbeat.

As an alternative to the use of electromagnetic sensors otherconventional techniques, such as ultrasound or magnetic resonanceimaging (MRI) can also be used for localization of catheter 10.

In addition, an impedance-based sensor can also be incorporated intocatheter 10. In an impedance-based system, several, such as three, highfrequency signals are generated along different axes. The catheterelectrodes may be used to sense these frequencies, and with appropriatefiltering, the strength of the signal and thus the position of thecatheter can be determined.

One skilled in the art will appreciate that the construction of catheter10 may be optimized to make use of the various localization techniques.

Endocardial and Epicardial Applications

Reference is now made to FIGS. 22, 23, and 24, which figures illustratehow the catheter of the present invention may be used in otherendocardial and epicardial applications.

Referring to FIG. 22, this figure illustrates an endocardial ablationprocedure. In this procedure, catheter shaft 12 is introduced into apatient's heart 150. Appropriate imaging guidance (direct visualassessment, camera port, fluoroscopy, echocardiographic, magneticresonance, etc.) can be used. FIG. 22 in particular illustrates cathetershaft 12 being placed in the left atrium of the patient's heart. Oncecatheter shaft 12 reaches the patient's left atrium, it may then beintroduced through an ostium 165 of a pulmonary vein 154. Asillustrated, braided conductive member 28 is then expanded to itsdeployed position, where, in the illustrated embodiment, braidedconductive member 28 forms a disk. Catheter shaft 12 is then advancedfurther into pulmonary vein 154 until the distal side 156 of braidedconductive member 28 makes contact with the ostium of pulmonary vein154. External pressure may be applied along catheter shaft 12 to achievethe desired level of contact of braided conductive member 28 with theostium tissue. Energy is then applied to the ostium tissue 165 incontact with braided conductive member 28 to create an annular lesion ator near the ostium. The energy used may be RF (radiofrequency), DC,microwave, ultrasonic, cryothermal, optical, etc.

Reference is now made to FIG. 23, which figure illustrates an epicardialablation procedure. As illustrated in FIG. 23, catheter shaft 12 isintroduced into a patient's thoracic cavity and directed to pulmonaryvein 154. Catheter 10 may be introduced through a trocar port orintraoperatively during open chest surgery Using a steering mechanism,preformed shape, or other means by which to make contact between braidedconductive member 128 and the outer surface 158 of pulmonary vein 154,braided conductive member 28 is brought into contact with the outersurface 158 of pulmonary vein 154. Appropriate imaging guidance (directvisual assessment, camera port, fluoroscopy, echocardiographic, magneticresonance, etc.) can be used. As illustrated in FIG. 23, in thisprocedure, braided conductive member 28 remains in its undeployed orunexpanded condition. External pressure maybe applied to achieve contactbetween braided conductive member 28 with pulmonary vein 154. Once thedesired contact with the outer surface 158 of pulmonary vein 154 isattained, ablation energy is applied to surface 158 via braidedconductive member 28 using, for example, RF, DC, ultrasound, microwave,cryothermal, or optical energy. Thereafter, braided conductive member 28may be moved around the circumference of pulmonary vein 154, and theablation procedure repeated. This procedure may be used to create, forexample, an annular lesion at or near the ostium.

Use of the illustrated endocardial or epicardial procedures may beeasier and faster than using a single “point” electrode since a completeannular lesion may be created in one application of RF energy.

Reference is now made to FIG. 24 which figure illustrates an endocardialmapping procedure. In the procedure illustrated in FIG. 24, cathetershaft 12 is introduced into pulmonary vein 154 in the manner describedin connection with FIG. 22. Once braided conductive 28 has reached adesired location within pulmonary vein 154, braided conductive member 28is expanded as described in connection with, for example, FIGS. 2-5until filaments 34 contact the inner wall 160 of pulmonary vein 154.Thereafter, electrical activity within pulmonary vein 154 may bedetected, measured, and recorded by an external device connected to thefilaments 34 of braided conductive member 28.

Access to the patient's heart can be accomplished via percutaneous,vascular, surgical (e.g. open-chest surgery), or transthoracicapproaches for either endocardial or epicardial mapping and/or mappingand ablation procedures.

The present invention is thus able to provide an electrophysiologycatheter capable of mapping and/or mapping and ablation operations. Inaddition, the catheter of the invention may be used to provide highdensity maps of a tissue region because electrocardiograms may beobtained from individual filaments 34 in braided conductive member 28 ineither a bipolar or unipolar mode.

Furthermore, the shape of the electrode region can be adjusted bycontrolling the radial expansion of braided conductive member 28 SO asto improve conformity with the patient's tissue or to provide a desiredmapping or ablation profile. Alternatively, braided conductive member 28may be fabricated of a material of sufficient flexural strength so thatthe tissue is preferentially conformed to match the expanded orpartially expanded shape of the braided conductive member 28.

The catheter of the present invention may be used for mappingprocedures, ablation procedures, and temperature measurement and controlon the distal and/or proximal facing sides of braided conductive member28 in its fully expanded positions as illustrated in, for example,FIG. 1. In addition, the catheter of the present invention can be usedto perform “radial” mapping procedures, ablation procedures, andtemperature measurement and control. That is, the outer circumferentialedge 76, illustrated, for example, in FIG. 8, can be applied against aninner circumferential surface of a blood vessel.

Furthermore, being able to use the same catheter for both mapping andablation procedures has the potential to reduce procedure time andreduce X-ray exposure.

The ability to expand braided conductive member 28 in an artery or veinagainst a tissue structure such as a freewall or ostium can provide goodcontact pressure for multiple electrodes and can provide an anatomicalanchor for stability. Temperature sensors can be positioned definitivelyagainst the endocardium to provide good thermal conduction to thetissue. Lesions can be selectively produced at various sections aroundthe circumference of braided conductive member 28 without having toreposition catheter 10. This can provide more accurate lesion placementwithin the artery or vein. Braided conductive member 28, in its radiallyexpanded position as illustrated in particular in FIGS. 1 and 8 isadvantageous because, in these embodiments, it does not block the bloodvessel during a mapping or ablation procedure, but allows blood flowthrough the braided conductive member thus allowing for longer mappingand/or ablation times, which can potentially improve accuracy of mappingand efficacy of lesion creation.

Methods Of Use

Reference is now made to FIGS. 25-31, which related to methods of usingthe catheter 10 described above. The methods are directed to thetreatment of a heart condition, e.g., atrial fibrillation, via themeasurement and ablation of inter-atrial conductive pathways.

FIG. 25A illustrates a portion of the conduction system of the heart150. The sinoatrial (SA) node 164, located at the top of the rightatrium 166, is the natural “pacemaker” of the heart. The SA node 164initiates the heartbeat by emitting an electrical signal that rapidlypropagates throughout the left atrium 168 and the right atrium 166, andcauses both atria to contract. The signal then travels to theatrioventricular (AV) node 170, located above the opening of thecoronary sinus in the inter-atrial septum of the right atrium 166. TheAV node propagates the signal to the muscle fibers of the rightventricle 172 and left ventricle 174, which then also contract. Thenormal sequence of electrical activation of the chambers of the heart iscalled sinus rhythm.

Abnormalities may exist in the heart's conduction rhythms. For example,atrial fibrillation is an abnormality of heart rhythm in which the atriaof the heart no longer contract in an organized manner. In atrialfibrillation, sinus rhythm does not occur. Instead, electrical impulsestravel randomly through the atria, leading to the activation ofdifferent parts of the atria at different times. The uncoordinatedactivation of the atria causes the walls of the atria quiver or“fibrillate.” Atrial fibrillation may result in a number of detrimentalconditions, including chest palpitations, stroke, and heart failure.

One treatment for atrial fibrillation is ablation, e.g., using RFenergy, of the tissues and pathways that give rise to the errantsignals. Ablation of the tissue alters the conductivity of the tissue.This may include suppressing, reducing, or eliminating the ability ofthe tissue to conduct or generate impulses. To detect foci thatoriginate errant signals or pathways that conduct errant signals,electrophysiological mapping may be performed. Electrophysiology studieshave revealed that the coronary sinus and fossa ovalis are potentialpathways for the conduction of errant impulses between the atria. Thecoronary sinus is a blood vessel that carries deoxygenated blood fromthe cardiac muscle tissue into the right atrium. The fossa ovalis is anoval depression on the lower part of the inter-atrial septum of theright atrium, and corresponds to the location of the foramen ovale inthe fetus. FIG. 25B illustrates the location of the fossa ovalis 176 andthe opening of the coronary sinus 178 in the right atrium 166.

According to the present invention, a catheter having a braidedconductive member, as described in connection with previous embodiments,may be used to ablate tissue at the fossa ovalis or coronary sinus toinhibit or reduce the conduction of electrical impulses in at least onedirection between the atria of the heart. Thus, a partial or completeblock of conduction may be formed. Further, the catheter may be used tomeasure signals or properties of the heart such as baseline electricalactivity, conduction via ablated pathways, and lesion quality. Oneadvantage of using a catheter according to the invention in thedescribed method is that only a single catheter is necessary to (1)create a lesion at the coronary sinus and/or fossa ovalis, and (2)perform any desired electrical measurements, such as to determine thequality of the lesion or the degree of conductivity of the coronarysinus or fossa ovalis. This avoids the need for changing catheters, forexample, between mapping and ablation procedures. It may also reduce thenumber of removal and reinsertion operations needed during anelectrophysiology study and treatment procedure.

Reference is now made to FIGS. 26A-C, which illustrate examples of theconduction of electrical impulses through the atria before ablation(FIG. 26A), after ablation at the coronary sinus (FIG. 26B), and afterablation at the fossa ovalis (FIG. 26C). Three preferential pathways forthe conduction of electrical signals are illustrated in FIG. 26A. Thesepathways are Bachmann's bundle 180, the fossa ovalis 182, and thecoronary sinus 184.

Bachmann's bundle 180 is a specialized path for inter-atrial conductionthat extends from the SA node 164 and is critical in propagating thesignal initiated by the SA node to the left atrium 168 to stimulatecontraction of the left atrium 168. While ablation of Bachmann's bundle180 may be beneficial in treating atrial fibrillation, ablation of thisarea may impair the normal conduction system of the heart. Inparticular, ablation of Bachmann's bundle 180 may result in inadequateactivation of the tissue on the atria, and a resultant inability of theatria to properly contract. Patients that undergo electricaldisconnection in this region typically need artificial activation of theatria (e.g., using a pacemaker) to sustain a normal heartbeat. Thus, itmay be advantageous to maintain the conduction pathway of Bachmann'sbundle 180 to retain the heart's ability to contract, and alter theconductivity of one or more alternative preferential inter-atrialconductive pathways. Ablation of one or more alternative inter-atrialconductive pathways may reduce or eliminate the occurrence of atrialfibrillation in the patient. Two such pathways, the fossa ovalis 182 andcoronary sinus 184, are discussed in connection with FIGS. 26B-C.However, it should be appreciated that other pathways may exist for thetransmission of errant impulses, and the invention is not limited toapplication at the described locations. Further, though ablation atBachmann's bundle 180 may have deleterious effects, there may becircumstances where such ablation may be beneficial and thus ablation ofBachmann's bundle 180 may be performed in accordance with the presentinvention.

FIG. 26B illustrates the conduction of electrical impulses through theatria after ablation of the coronary sinus 184 at a lesion location 186.While signals may travel from the right and left atria into the coronarysinus 184, conduction in at least one direction across lesion location186 is reduced or eliminated. By ablating the coronary sinus pathway184, the inter-atrial conduction of errant signals via the coronarysinus 184 may be reduced or eliminated, thereby reducing or eliminatingatrial fibrillation. As shown, the conductive pathways of Bachmann'sbundle 180 and the fossa ovalis 182 are maintained.

FIG. 26C illustrates the conduction of electrical impulses through theatria after ablation of the fossa ovalis 182 at a lesion location 188.Conduction across lesion location 186 is reduced or eliminated in atleast one direction after ablation at the fossa ovalis 182. By ablatingthe fossa ovalis pathway 182, the inter-atrial conduction of errantsignals, and hence atrial fibrillation, may be reduced or eliminated. Asshown, the conductive pathways of Bachmann's bundle 180 and coronarysinus 184 are maintained.

To determine one or more pathways for ablation, a physician may measureheart signals during atrial fibrillation, which represents a baselineanalysis. Baseline analysis may be performed, for example, usingelectrodes positioned such that the direction of propagation of signalscan be determined at locations in the heart, including the atria and/orventricles. The baseline information indicates which pathways, if any,conduct errant signals. Ablation may be performed at one or both of thecoronary sinus 184 and fossa ovalis 182 in accordance with the presentinvention. For example, ablation at the coronary sinus 184 alone may besufficient for treatment of atrial fibrillation in a particular patient.In addition to being used to determine an ablation site, baseline heartsignal characteristics may be compared with post-ablation heart signalcharacteristics to provide an indication of success of ablation. Inparticular, the activation sequence of the heart tissue will change in apredictable manner after successful ablation of a pathway. According toone embodiment of the present invention, baseline analysis may bepreformed using a catheter, as described herein, that may also be usedfor ablation.

As discussed above, after ablation of a pathway, it is desirable toconfirm that the desired amount of conductive alteration of the pathwayhas been achieved. One way this can be achieved is by emitting anelectrical signal on one side of the lesion and detecting a receivedelectrical signal on the other side of the lesion. The degree to whichthe signal is propagated across the lesion indicates the conductivealteration of the pathway. However, during the ablation process it maybe useful to obtain a preliminary indication of the conductivealteration of the pathway. The quality of the lesion formed duringablation correlates well with the degree of conductive alteration of thepathway, and may be easier to measure. Lesion quality may be determinedby measuring electrical signals within the lesion itself to determinethe strength of the electrical signals in the lesion and/or theimpedance of the tissue in the lesion. In general, the higher the lesionquality, the higher the degree of conductive alteration of the pathway.According to one embodiment of the present invention, the degree ofconductive alteration of a pathway and/or the quality of a lesion may bemeasured using a catheter, as described herein, that may also be usedfor ablation.

Having thus described several features of the catheter 10, variousmethods for using the catheter 10 will be described. Reference is nowmade to FIGS. 27A-C, which illustrate a method of using catheter 10having a braided conductive member 28 to perform ablation and/or mappingat the ostium 192 of the coronary sinus 178 in the right atrium 166.Catheter 10 is first introduced into the right atrium 166 with thebraided conductive member 28 in an undeployed position, as shown in FIG.27A. A steerable portion 194 is shown on catheter 10, proximal to thebraided conductive member 28. While the catheter 10 of FIGS. 27A-C isshown as having a steerable portion 194 located proximal to the braidedconductive member 28, it is not necessary to performing the method ofFIGS. 27A-C. Further, though steerable portion 194 is not shown inconnection with other embodiments, it should be appreciated that any ofthe embodiments described herein may employ proximal steering, distalsteering, or any combination.

As shown in FIG. 27B, the braided conductive member 28 is deployed inthe right atrium 166. The braided conductive member 28 may be partiallyor fully deployed. Further, the deployed braided conductive member 28may assume any number of shapes or configurations. For example, thebraided conductive member 28 may have a non-circular edge in thedeployed configuration, as shown in FIG. 15A, or may have an asymmetricshape in the deployed configuration, as shown in FIG. 15B. In anotherexample, the braided conductive member 28 may be deformable, as shown inU.S. Pat. No. 6,315,778 which is hereby incorporated by reference. Thecatheter 10 may assume any number of alternate configurations. Forexample, the catheter 10 may not include distal tip portion 18, as shownin FIGS. 16A-16C. It should be appreciated that the variations describedabove may be incorporated in any of the embodiments described herein.

The distal tip portion 18 of catheter 10 is then maneuvered into thecoronary sinus 178 until the braided conductive member 28 is near or incontact with cardiac tissue 190 at the ostium 192 of the coronary sinus178, as shown in FIG. 27C. The distal tip potion 18 advantageously aidsin positioning the braided conductive member 28 at the ostium 192 and instabilizing the braided conductive member 28 at that location. Themaneuverability of the catheter 10 proximal to the braided conductivemember 28 also aids in the positioning of the braided conductive member28. Once the braided conductive member 28 is positioned, ablative energymay then applied to the ostium 192 via the braided conductive member 28.Braided conductive member 28 may form a ring-shaped lesion around theopening of the coronary sinus 178, although the lesion need not becomplete. A lesion of any shape that substantially or sufficientlyinhibits the inter-atrial conduction via the coronary sinus 178 in atleast one direction may successfully reduce or inhibit atrialfibrillation.

For this and other embodiments, it should be appreciated that theablation may be tuned for a specific application by adjusting specifiedparameters. For example, power, temperature, duration of application,and number of RF applications may all be varied to achieve desiredresults, as is well known in the art.

The braided conductive member 28 of this embodiment may be specializedfor ablation at the ostium 192 of the coronary sinus 178. For example,insulation may be selectively removed from the filaments of the braidedconductive member 28 on the distal side 196 of braided conductive member29. Temperature sensors may be incorporated in the braided conductivemember 28, as described herein, and may be used to indicate thetemperature of the tissue during ablation. In addition to serving anablative function, the braided conductive member 28 may also be used toassess the quality of the lesion at the ostium 192 and/or theconductivity via the coronary sinus 178 before or after ablation.

Reference is now made to FIGS. 28A-B, which illustrate a method of usinga catheter 10 having a braided conductive member 28 to perform ablationand/or mapping at a location of the wall 198 of the coronary sinus 178.Catheter 10 is first introduced into the right atrium 166 with thebraided conductive member 28 in an undeployed position. Next, the distaltip portion 18 and braided conductive member 28 of the catheter 10 areinserted into the coronary sinus 178, as shown in FIG. 28A.

When the braided conductive member 28 is aligned with the desiredablation location, the braided conductive member 28 is deployed in sothat it is in contact with the wall 198 of the coronary sinus 178. Oncethe braided conductive member 28 is deployed, ablative energy may beapplied to the wall 198 of the coronary sinus 178 via the braidedconductive member 28, or electrical measurements may be performed usingbraided conductive member 28. In FIG. 28B, the braided conductive member28 is partially deployed, and the braided conductive member 28 is incontact with a band-shaped region of the coronary sinus 178. However,the braided conductive member may be fully deployed, and may be incontact with a narrower ring-shaped region of the coronary sinus 178.The size of the braided conductive member may be chosen according to theshape of the region desired to be ablated, as well as other factors.Further, as discussed in connection with the embodiment of FIGS. 27A-C,the deployed braided conductive member 28 may assume any number ofshapes or configurations.

The braided conductive member 28 of this embodiment may be specializedfor ablation of the wall 198 of the coronary sinus 178. For example,insulation may be removed from the filaments of the braided conductivemember 28 near the circumferential region 204 of the braided conductivemember 28 that contacts the wall 198 of the coronary sinus 17.Temperature sensors may be incorporated into the braided conductivemember 28, as discussed above. Further as discussed above, the braidedconductive member 28 may be used to assess the quality of the lesion atthe wall 198 of the coronary sinus 178 and/or the conductivity via thecoronary sinus 178.

Reference is now made to FIGS. 29A-B, which illustrate a method of usinga catheter 10 having a braided conductive member 28 to perform ablationand/or mapping at the fossa ovalis 176 in the right atrium 166. Thefossa ovalis 176 is an area of the inter-atrial septum 200 having adecreased thickness relative to surrounding areas. Because the surfaceof the inter-atrial septum 200 at the location of the fossa ovalis 176is smooth, it is difficult to form good contact between an electrode andthe fossa ovalis 176. Loss of contact between the electrode and thefossa ovalis 176 during ablation can have serious negative effects,including accidental ablation of the nearby AV node. Thus, according toone embodiment of the invention, a puncture 202 may be made in theinter-atrial septum 200 at the fossa ovalis 176. The puncture may beformed, for example, using a needle-bearing catheter. The puncture 202may be used to accommodate a distal tip portion 18 of the catheter 10,and thereby hinder movement of the catheter 10 during ablation ormapping.

Catheter 10 is introduced into the right atrium 166, where the braidedconductive member 28 is deployed. The braided conductive member 28 maybe partially or fully deployed and may have any of a number ofconfigurations as described above. Next, as shown in FIG. 29A, thedistal tip portion 18 of catheter 10 is passed from the right atrium 166to the left atrium 168 through the inter-atrial septum 200. The catheter10 is advanced in the direction of inter-atrial septum 200 until thedistal side 196 of the braided conductive member 28 contacts theinter-atrial septum 200 of the right atrium 166 at the fossa ovalis 176.

The braided conductive member 28 of this embodiment may be specializedfor ablation at the right atrium wall of the fossa ovalis 176. Forexample, as discussed in connection with the embodiment of FIGS. 27A-C,insulation may be selectively removed from the filaments of the braidedconductive member 28 on the distal side 196 of braided conductive member28. Temperature sensors may also be incorporated in the braidedconductive member 28. The braided conductive member 28 may be used toassess the quality of the lesion at the fossa ovalis 176 and/or theconductivity via the fossa ovalis 176.

Reference is now made to FIGS. 30A-C, which illustrate a method of usinga catheter 10 having a braided conductive member 28 to perform ablationand/or mapping at the fossa ovalis 176 in the left atrium 168. Asdiscussed in connection with the embodiment of FIGS. 29A-B, the surfaceof the inter-atrial septum 200 at the location of the fossa ovalis 176is smooth, and it is therefore difficult to form good contact between anelectrode and the fossa ovalis 176. Thus, according to one embodiment ofthe invention, a puncture 202 may be made in the inter-atrial septum 200at the fossa ovalis 176, through which a portion of catheter 10 may bepassed. In the example of FIGS. 30A-C, a distal tip portion 18 andbraided conductive member 28 of catheter 10 are passed through thepuncture 202 into the left atrium.

Catheter 10 is introduced into the right atrium 166 with the braidedconductive member 28 in an undeployed position. Next, as shown in FIG.30A, the distal top portion 18 and braided conductive member 28 ofcatheter 10 are passed from the right atrium 166 to the left atrium 168through the inter-atrial septum 200. Once in the left atrium 168, thebraided conductive member 28 is deployed. The braided conductive member28 may be partially or fully deployed and may have any of a number ofconfigurations as described above. Further, temperature sensors may beincorporated in the braided conductive member 28.

As shown in FIG. 30B, once the braided conductive member 28 is deployed,the catheter 10 is pulled back towards the right atrium 166. Thecatheter 10 is retracted in the direction of inter-atrial septum 200until the proximal side 206 of the braided conductive member 28 contactsthe inter-atrial septum 200 of the left atrium 168 at the fossa ovalis176. When the braided conductive member 28 is near or in contact withthe inter-atrial septum 200, ablative energy may be applied to the fossaovalis 176 via the braided conductive member.

The braided conductive member 28 of this embodiment may be specializedfor ablation at the right atrium wall of the fossa ovalis 176. Forexample, as discussed in connection with the embodiment of FIGS. 27A-C,insulation may be selectively removed from the filaments of the braidedconductive member 28 on the distal side 196 of braided conductive member29. The braided conductive member 28 may also be used to assess thequality of the lesion at the fossa ovalis 176 and/or the conductivityvia the fossa ovalis 176.

Reference is now made to FIGS. 31A-B, which illustrate a method of usinga catheter 10 having a proximal braided conductive member 28 a and adistal braided conductive member 28 b to perform ablation and/or mappingat the fossa ovalis 176 in the right atrium 166 and left atrium 168,respectively. Both braided conductive members 28 a-28 b are undeployedwhen the catheter 10 is introduced into the right atrium 166. Asdescribed in connection with the embodiment of FIGS. 30A-C, the distaltip portion 18 and distal braided conductive member 28 b of catheter 10may be passed through the puncture 202 in inter-atrial septum 200 intothe left atrium 168. The distal braided conductive member 28 b is thendeployed is the left atrium 168. The distal braided conductive member 28b may be partially or fully deployed and may have any of a number ofconfigurations as described above. Further, temperature sensors may beincorporated in the distal braided conductive member 28 b. Once thedistal braided conductive member 28 b is deployed, the catheter 10 ispulled back towards the right atrium 166. The catheter 10 is retractedin the direction of inter-atrial septum 200 until the proximal side 206of the distal braided conductive member 28 b contacts the inter-atrialseptum 200 of the left atrium 168 at the fossa ovalis 176, as shown inFIG. 31A.

Next, the proximal braided conductive member 28 a is deployed in theright atrium 166. Similarly, the proximal braided conductive member 28 amay be partially or fully deployed and may have any of a number ofconfigurations as described above. The distal braided conductive member28 b may be deployed by compression in a distal-to-proximal direction,while the proximal braided conductive member 28 a may be deployed bycompression in a proximal-to-distal direction. Thus, when proximalbraided conductive member 28 a is deployed, it contacts the inter-atrialseptum 200 of the right atrium 166 at the fossa ovalis 176, as shown inFIG. 31B.

When the braided conductive members 28 a-28 b are near or in contactwith the inter-atrial septum 200, ablative energy may be applied fromboth atria to the fossa ovalis 176 via the braided conductive members 28a-28 b. The proximal and distal braided conductive members 28 a-28 b mayhave insulation that is selectively removed from the filaments on thedistal side 196 and proximal side 206 of the proximal and distal braidedconductive members 28 a-28 b, respectively. The braided conductivemembers 28 a-28 b, either alone or in combination, may also be used toassess the quality of the lesion at the fossa ovalis 176 and/or theconductivity via the fossa ovalis 176.

For any of the above described methods, it should be appreciated thatappropriate imaging guidance (direct visual assessment, camera,fluoroscopy, echocardiographic, magnetic resonance, etc.) may be used toassist in positioning of the braided conductive member 28 relative to atarget ablation or measurement site.

Shaft electrodes

Reference is now made to FIG. 32, which illustrates a catheter 10 havinga braided conductive member 28 and electrodes disposed on the shaft 12of the catheter. The catheter 10 of FIG. 32 includes two electrodes onthe distal tip portion 18 of the catheter 10, an electrode 210 on thedistal tip and an electrode 212 proximal to the electrode 210. Further,the catheter 10 includes electrodes 214 a-c, proximal to the braidedconductive member 28. Although a particular electrode configuration isillustrated, it should be appreciated that the invention is not limitedto this configuration, and that many alternative types and placements ofelectrodes are possible. Further, though electrodes are not illustratedon the shaft 12 of the catheter 10 of other embodiments herein, any ofthe described embodiments may or may not include such electrodes.

The electrodes on the shaft 12 of the catheter 10 may perform mappingfunctions, such as performing a baseline analysis of the electricalconductivity of the heart or assessing the conductivity of an electricalpathway. For example, electrodes 214 a-c may be used to select a pathwayfor ablation. When the catheter 10 is in the right atrium for example,the shaft 12 may be positioned so that the electrodes 214 a-c contactthe right atrium at various points. Based on the electrical signalreceived at each, and the time of receipt of the signal by eachelectrode, the direction of propagation of the electrical impulses inthe right atrium can be measured. This data may be used to determine theconductive pathways of the heart and, thereby, locations for ablation.

With successful coronary sinus ablation, the activation sequence of thenear field coronary sinus musculature will change from an “ostium todistal” sequence (before ablation) to a “distal to ostium” sequence(after ablation). The coronary sinus will be activated via distal leftatrium to coronary sinus connections. With successful fossa ovalisablation after successful coronary sinus ablation, the left atriumactivation sequence will change from a “septal to lateral” sequence(before ablation) to a “lateral to septal” sequence (after ablation)since the left atrial activation is still intact via Bachmann's Bundleand thus proceeds from cranial to caudal. The electrodes 214 a-c may beused as described above to determine the activation sequence of theheart after ablation of the coronary sinus and/or fossa ovalis, andthereby determine the degree of conductive alteration of these pathways.

A pair of electrodes, e.g., electrodes 214 c and 212, may be used tomeasure the conductivity of an electrical pathway before or afterablation. For example, electrode 212 may be designated as a pacingelectrode and electrode 214 c may be designated as a measurementelectrode. The electrodes may be placed in contact with the cardiactissue in a conductive pathway. The pacing electrode emits a signal fordetection by the measurement electrode. Before ablation of a pathway,the heart tissue will be healthy and a strong signal will be received bythe measurement electrode based on the emitted signal. However, if apathway has been successfully conductively altered due to ablation, asignal emitted by the pacing electrode will be received very weakly ornot at all by the measurement electrode. Thus, electrodes on the shaft12 of the catheter 10 may be used to measure the conductivity of anablated pathway.

A distal tip electrode 210 is also shown which may perform any number offunctions. For example, the distal tip electrode 210 may be used as aunipolar electrode to detect an electrocardiogram at a location of theheart tissue or may be used as a reference electrode.

Experimental Data

Catheter ablation of an inter-atrial conduction path for treatment ofatrial fibrillation was investigated in a dog study. Under fluoroscopicguidance and ICE (Acuson), a multi-polar electrode catheter was placedin the CS of dogs. The activation sequence was assessed during low rightatrial (LRA) pacing. The CS catheter was then replaced with a mesh typeelectrode. RF energy was delivered just outside and just inside the CSos. After each ablation the CS mapping catheter was repositioned andactivation sequence reevaluated. Pre and post-ablation recordings werealso performed with the mesh type. CS access was achieved in 3 of 4dogs. CS activation sequence during LRA pacing was proximal to distal(CS 8,9 to CS 1,2) in all animals (see FIG. 33). In addition, far field(low frequency) left atrial potentials were seen. After RF ablation theCS activation sequence was distal to proximal, consistent withconduction block in the CS (see FIG. 34). Macroscopic lesion evaluationshowed circumferential lesions just inside the CS os.

Having thus described at least one illustrative embodiment of theinvention, various alterations, modifications, and improvements willreadily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to be within the spirit andscope of the invention. Accordingly, the foregoing description is by wayof example only and is not intended as limiting. The invention islimited only as defined in the following claims and the equivalentsthereto.

1. A method for treating a condition of the heart, comprising acts of:introducing a catheter into the heart, the catheter having a braidedconductive member comprising a plurality of partially insulatedfilaments at a distal end thereof, wherein the braided conductive membercomprises an ablative ring comprising uninsulated portions of filamentshaving a generally ring-shaped configuration; expanding the braidedconductive member into a deployed configuration; contacting a selectedlocation of the heart with the braided conductive member; forming alesion on tissue at the selected location of the heart by energizing aplurality of filaments of the braided conductive member; and measuringthe quality of the lesion using at least one filament of the braidedconductive member.
 2. The method of claim 1, wherein the act of forminga lesion on tissue at a selected location of the heart with the braidedconductive member and the act of measuring the quality of the lesionwith the braided conductive member are performed concurrently.
 3. Themethod of claim 1, wherein the act of measuring the quality of thelesion with the braided conductive member includes measuring theimpedance of the tissue at the selected location.
 4. The method of claim1, wherein the act of measuring the quality of the lesion with thebraided conductive member includes measuring an amplitude of anelectrical signal at the selected location.
 5. The method of claim 1,wherein the ablative ring comprises a first uninsulated portion incontact with a second uninsulated portion adjacent to the firstuninsulated portion.
 6. The method of claim 1, wherein the ablative ringis distally-facing.
 7. A method of operating a heart catheter having abraided conductive member comprising a plurality of partially insulatedfilaments, the braided conductive member comprising a plurality ofablation filaments for applying ablative energy to a surface of a heart,the plurality of ablation filaments comprising a first ablation filamenthaving a first uninsulated portion and a second ablation filament havinga second uninsulated portion in contact with the first portion when thebraided conductive member is in a deployed configuration, and one ormore mapping filaments for measuring an electrical signal at a surfaceof the heart, the method comprising expanding the braided conductivemember into the deployed configuration, contacting a selected locationof the heart with the braided conductive member, and activating theplurality of ablation filaments and the one or more mapping filamentsconcurrently.
 8. The method of claim 7, wherein the heart catheterfurther includes means for steering the heart catheter.
 9. The method ofclaim 8, wherein the means for steering the heart catheter includesmeans for manipulating a portion of the heart catheter to form a curvethat is proximal to the braided conductive member.
 10. The method ofclaim 7, wherein the braided conductive member comprises an ablativering comprising uninsulated portions of filaments having a generallyring-shaped configuration, wherein the uninsulated portions comprise thefirst and second uninsulated portions.
 11. The method of claim 10,wherein the ablative ring is distally-facing.
 12. A method for treatinga condition of a heart, comprising an act of: using a catheter having anexpandable braided conductive member comprising a distally-facingablative ring comprising uninsulated portions of filaments having agenerally ring-shaped configuration to create a lesion at a wall of theright atrium at the fossa ovalis and/or a wall of the left atrium at thefossa ovalis, wherein the lesion is formed by the distally-facingablative ring.
 13. The method of claim 12, wherein the act of using thecatheter further comprises using the distally-facing ablative ring tocreate a lesion at a wall of the coronary sinus.
 14. The method of claim13, further including an act of assessing the conductive alteration ofthe coronary sinus.
 15. The method of claim 12, wherein the act of usingthe catheter further comprises using the distally-facing ablative ringto create a lesion at a wall of the right atrium at an opening of thecoronary sinus.
 16. The method of claim 15, further including an act ofassessing the conductive alteration of the coronary sinus.
 17. Themethod of claim 12, wherein the act of using the catheter furthercomprises using the distally-facing ablative ring to create a lesion ata wall of the right atrium at the fossa ovalis.
 18. The method of claim12, wherein the act of using the catheter further comprises using thedistally-facing ablative ring to create a lesion at a wall of the leftatrium at the fossa ovalis.
 19. The method of claim 12, furtherincluding an act of reducing electrical conduction between the rightatrium and left atrium of the heart.
 20. The method of claim 19, furtherincluding an act of using the catheter to measure the electricalconduction between the right atrium and left atrium of the heart. 21.The method of claim 12, wherein the act of using the catheter comprisesapplying RF energy.
 22. The method of claim 12, further including an actof using the catheter to measure a quality of the lesion.
 23. A methodfor treating atrial fibrillation in a heart, comprising acts of:introducing a catheter into the heart, the catheter having a braidedconductive member comprising a plurality of partially insulatedfilaments at a distal end thereof, wherein the braided conductive membercomprises an ablative ring comprising uninsulated portions of filamentshaving a generally ring-shaped configuration; expanding the braidedconductive member into a deployed configuration; contacting a selectedlocation of the heart with the braided conductive member; and using thebraided conductive member to ablate a region of the heart that serves asan electrical pathway between that left atrium and the right atrium ofthe heart to alter the conductivity of the electrical pathway.
 24. Themethod of claim 23, wherein the act of using the catheter includes usingthe braided conductive member to ablate the coronary sinus.
 25. Themethod of claim 24, wherein the act of using the catheter includes usingthe braided conductive member to reduce an electrical conductivity ofthe coronary sinus.
 26. The method of claim 23, wherein the act of usingthe catheter includes using the braided conductive member to ablate thefossa ovalis.
 27. The method of claim 26, wherein the act of using thecatheter includes using the braided conductive member to reduce anelectrical conductivity of the fossa ovalis.
 28. The method of claim 23,wherein the ablative ring comprises a first uninsulated portion incontact with a second uninsulated portion adjacent to the firstuninsulated portion.
 29. The method of claim 23, wherein the ablativering is distally-facing.